JP5773350B2 - Method for storing and / or separating oxygen using brown mirrorite type manganese oxide - Google Patents

Description

  The present invention has an oxygen absorption / release function, a catalyst material for exhaust gas purification, a catalyst material for redox, a positive electrode material for a solid oxide fuel cell, an oxygen separator, an oxygen remover, an oxygen selector, The present invention relates to a brown mirrorlite type manganese oxide that can be used in an oxygen enrichment device or the like.

  Oxygen, the most familiar element, is deeply involved in chemical reactions in energy production, industrial production, life activities, etc. In recent years, with the development of science and technology, the oxidation-reduction reaction is precisely controlled to increase productivity. There is a strong demand for higher levels and contributions to environmental protection.

  To meet these demands, oxygen storage materials with the ability to reversibly absorb and release oxygen have attracted attention. Catalyst materials for exhaust gas purification, catalyst materials for redox, solid oxide fuels Applications to battery positive electrode materials, oxygen separators, oxygen removers, oxygen selectors, oxygen enrichers and the like are expected.

Currently, CeO ₂ —ZrO ₂ (see Patent Document 1) and Ln ₂ O ₂ SO ₄ —Ln ₂ O ₂ S (see Patent Document 2 and Non-Patent Documents 1 to 4) are known as oxygen storage materials. It has been. CeO ₂ —ZrO ₂ (hereinafter sometimes simply referred to as “CZ”) has already been widely put into practical use as an exhaust gas purification catalyst (see Non-Patent Documents 5 to 7).

  The performance of the oxygen storage material is evaluated by an index of “oxygen storage capacity” (= Oxygen Storage Capacity = OSC). OSC is a value indicating the amount of absorbed oxygen per unit material amount.

The theoretical value of OSC (oxygen storage capacity) of CZ is 2.8 wt% (see the following formula), but it is actually about 2.2 wt% (see Non-Patent Document 7), which is not always sufficient. is not. CZ requires a strong reducing atmosphere for releasing oxygen, and oxygen cannot be released only by heating. Therefore, it is difficult in principle to use CZ in the oxygen enrichment technology field for increasing the oxygen concentration, and its use is limited.
Ce _0.5 Zr _0.5 O _1.75 +1/8 O ₂ = Ce _0.5 Zr _0.5 O ₂

Ln ₂ O ₂ SO ₄ -Ln ₂ O ₂ S has a very high OSC of 18.7 wt% and can store a large amount of oxygen, but (a) operates only in a high temperature region (600 ° C.-). (B) As with CZ, a strong reducing atmosphere is required for oxygen release, and (c) S is gradually evaporated and loses activity in repeated operations, so cycle characteristics are good. I have problems such as not.

In addition to the above oxide, as an oxygen storage material, A _j B _k C _m D _n O _{7 + δ} (A: one or more of trivalent rare earth elements and Ca, B: one of alkaline earth metal elements) Species or two or more, C, D: one or more of oxygen tetracoordinate elements, at least one of which is a transition metal element, provided that j> 0, k> 0, each independently m ≧ 0 , N ≧ 0, and j + k + m + n = 6, 0 <δ ≦ 1.5.) (See Patent Document 3 and Non-Patent Document 8).

Among the above oxides, YBaCo ₄ O _{7 + δ} is a promising material as a practical material because it has a sufficient oxygen storage capacity, operates at 400 ° C. or less, and has a good response to changes in oxygen partial pressure. However, YBaCo ₄ O _{7 + δ} is chemically unstable in a high temperature range, and is not necessarily an optimum substance as an exhaust gas purifying catalyst exposed to a high temperature. YBaCo ₄ O _{7 + δ} is not necessarily an optimal substance as a practical catalyst material because it contains valuable Co as a constituent component.

In light of the above, the present applicant has proposed that the oxygen-deficient perovskite-type metal oxide “(Ba _1−x A _x ) B (Mn _2−y C _y ) O _{5 + δ} [A: alkaline earth metal other than Ba”. 1 type or 2 types or more, B: Y, 1 type or 2 types of rare earth elements, and Ca, 1 type or 2 types of C: Fe and Co] are proposed (see Patent Document 4).

  The oxygen-deficient perovskite metal oxide is a substance that absorbs oxygen very quickly and has an excellent oxygen storage capacity. However, in addition to the problem that (i) synthesis is difficult, (ii) as well as CZ, it is highly resistant to oxygen release. Since a reducing atmosphere is required, there is a problem that it is difficult to apply to an oxygen enricher.

Further, Patent Document _{5, (Ln 1-x A} x) (B y Fe 1-y) O 3 or _{(Ca 1-x A x)} (B y Fe 1-y) O 2.5, oxygen concentrator It has been proposed to be used as a ceramic material. However, Patent Document 5 does not describe the specific chemical composition of (Ca _1−x A _x ) (B _y Fe _1−y ) O _2.5 , and further describes the evaluation of oxygen storage capacity. Absent.

  In any case, substances applicable to exhaust gas purification catalyst materials, oxidation-reduction catalyst materials, positive electrode materials for solid oxide fuel cells, oxygen separation devices, oxygen removal devices, oxygen selection devices, oxygen enrichment devices, etc. (B) Oxygen absorption / release characteristics different from CZ (with high temperature storage capacity (OSC) and chemical stability in high temperature range). And (c) the appearance of inexpensive and practical metal oxides that do not contain expensive elements as constituents.

JP 2005-119949 A JP 2008-284512 A International Publication WO2007 / 004681 Japanese Patent Application No. 2009-161964 JP 2009-227553 A

Yasuyuki Sakamoto et al., R & D Review of Toyota CRDL 37, 14 (2002) M. Machida et al., Chem. Commun. 662 (2004) M. Machida et al., Chem. Mater. 17, 1487 (2004) K. Ikeue et al., J. Catalysis 248, 46 (2007) M. Ozawa et al., J. Alloys and Compd. 193, 73 (1993) Y. Nagai et al., Catalysis Today 74, 225 (2002) “Cerium is interesting now” (Tea I Sea Publishing, 2005) M. Karppinen et., Chem. Mater. 18, 490 (2006) A. J. Wright et al., J. Mater. Chem. 12, 978 (2002) H. M. Palmer et al., Chem. Mater. 18, 1130 (2006)

  In view of the above demand, the present invention is directed to a catalyst material for exhaust gas purification, a catalyst material for redox, a positive electrode material for a solid oxide fuel cell, an oxygen separator, an oxygen remover, an oxygen selector, an oxygen enricher, and the like. Applicable substances are (a) large oxygen storage capacity and high-temperature chemical stability, and (b) oxygen / release function different from CZ (absorbs and releases oxygen only by temperature change) And (c) an inexpensive and practical metal oxide that does not contain an expensive element as a constituent component.

  Furthermore, this invention makes it a subject to provide the method and apparatus which utilize effectively the metal oxide which has the outstanding oxygen storage ability.

The present inventors diligently searched for a metal oxide having an oxygen storage capacity comparable to that of CeO ₂ —ZrO ₂ (CZ) or YBaCo ₄ O _{7 + δ} . As a result, Ca ₂ AlMnO _{5 + δ} (δ = 0 to 0.5) (see Non-Patent Documents 9 and 10), which is a kind of brown mirrorite type manganese oxide, has unique oxygen absorption / release characteristics. At the same time, the present inventors have found that it has an excellent oxygen storage capacity (3.3 wt%) and is a promising substance as a novel oxygen storage material that can be used in various technical fields.

  The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) A method for storing and / or separating oxygen using a brown mirrorlite type manganese oxide of the following formula (1) , wherein the manganese is repeatedly changed in a temperature range of 400 to 600 ° C. A method for storing and / or separating oxygen, wherein the amount of oxygen is changed and the oxygen is stored and / or separated in a range of more than 0 to 10 mol% with respect to the total amount of oxygen in the oxide.
(Ca _2−x A _x ) (Mn _2−y B _y ) O _{5 + δ} (1)
Here, A: one or more of alkaline earth metals other than Ca
B: One or more of Al, Fe, Co, and Ga
0 ≦ x ≦ 2
0 ≦ y <2
0 ≦ δ ≦ 0.5
(2) The oxygen storage / separation method according to (1), wherein x and y are 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1, respectively.

The manganese oxide “(Ca _2−x A _x ) (Mn _2−y B _y ) O _{5 + δ} (δ: 0 ≦ δ ≦ 0.5)” of the present invention absorbs and releases oxygen even with only a temperature change. In addition to the catalyst material for exhaust gas purification, the catalyst material for redox, the cathode material of the solid oxide fuel cell, oxygen storage, oxygen separation, oxygen removal, oxygen selection, and / or oxygen It is the most suitable material for enrichment.

  Further, the manganese oxide of the present invention is a promising substance as an inexpensive practical material that replaces CZ containing expensive Ce because it contains abundant elements as resources.

It is a figure which shows a brown mirror light type crystal structure. Is a diagram showing the crystal structure of Ca ₂ AlMnO _{5 + δ.} (A) shows the crystal structure of Ca ₂ AlMnO _5.0 , and (b) shows the crystal structure of Ca ₂ AlMnO _5.5 . An X-ray diffraction pattern (above) of Ca ₂ AlMnO _5.0 synthesized by solid phase reaction using CaCO ₃ , Al ₂ O ₃ , and Mn ₂ O ₃ as starting materials, and CaCO ₃ , Al, and Mn ₂ O ₃ was used as a starting material, is a diagram showing an X-ray diffraction pattern of Ca ₂ AlMnO _5.0 synthesized in EDTA complex polymerization reaction (below). The Ca ₂ AlMnO _5.0, heated in an oxygen stream, then cooled, shows a weight change rate when given heat history. It is a diagram showing an X-ray diffraction pattern of Ca ₂ AlMnO _{5 +} δ longitudinal thermogravimetric analysis. In the figure, the upper is an X-ray diffraction pattern before thermogravimetric analysis, and the lower is an X-ray diffraction pattern after thermogravimetric analysis. It is a figure which shows the result (weight change rate (DELTA) W) of the thermogravimetric analysis which carried out by switching atmosphere to nitrogen atmosphere and oxygen atmosphere alternately, fixing atmospheric temperature to 500 degreeC. It is a figure which shows the change of (DELTA) W when temperature is changed repeatedly between 500 degreeC and 600 degreeC in oxygen stream.

The manganese oxide of the present invention “(Ca _2−x A _x ) (Mn _2−y B _y ) O _{5 + δ} ” (hereinafter sometimes referred to as “the oxide of the present invention”) has a brown mirrorite crystal structure. However, unlike the known CZ, it is a substance having oxygen absorption / release characteristics that function only by temperature change. This is a feature of the oxide of the present invention.

  That is, the oxide of the present invention incorporates oxygen into the crystal lattice at a low temperature range of about 600 ° C. or lower in an oxygen atmosphere (0.5 ≧ δ> 0), and the crystal lattice at a high temperature range higher than about 600 ° C. It has a characteristic of releasing oxygen taken in.

FIG. 1 shows a brown mirrorlite type crystal structure. The fact that the oxide of the present invention has an oxygen absorption / release function different from that of CZ means that the redox couple of metal elements is different (in the oxide of the present invention, Mn ³⁺ / Mn ⁴⁺ , in CZ, Ce ³⁺ / In addition to Ce ⁴⁺ ), it is closely related to the crystal structure.

FIG. 2 shows the crystal structure of Ca ₂ AlMnO _{5 + δ} . 2A shows the crystal structure of Ca ₂ AlMnO _5.0 before absorbing oxygen, and FIG. 2B shows the crystal structure of Ca ₂ AlMnO _5.5 that absorbed oxygen. The brown mirrorite crystal structure includes an oxygen deficient layer that is a two-dimensional oxygen ion conduction path, and this oxygen deficient layer contributes greatly to the absorption and release of oxygen in a milder environment. it is conceivable that.

  The oxide of the present invention can be synthesized by baking a precursor prepared by an EDTA complex polymerization method at a high temperature.

For example, using CaCO ₃ , Al (powder), and Mn ₂ O ₃ as starting materials, a predetermined amount of these powders are dissolved in concentrated nitric acid, and complexed by adding an EDTA / NH ₃ solution. The molar ratio of EDTA to metal ions is 1.5: 1. After adjusting the pH of the EDTA complex solution to 8-9, for example, pH = 9, it is heated to 100-140 ° C., for example, 120 ° C., dried, and further combusted to produce a porous combustion product. (Precursor) is prepared.

  The combustion product (precursor) is calcined in air at 430 to 470 ° C., for example, 450 ° C., and further in air at 1200 to 1300 ° C. for several tens of hours, for example, 1250 ° C. for 24 hours. The main oxide is fired to synthesize the oxide of the present invention. The obtained oxide of the present invention is subjected to phase identification and structural analysis by X-ray diffraction, and thermogravimetric analysis is performed using a thermobalance to evaluate oxygen absorption / release characteristics.

The oxide of the present invention can also be synthesized by a solid phase reaction method using Al ₂ O ₃ (powder) instead of Al (powder), but the reaction does not proceed sufficiently and unreacted substances are used as impurities. May remain. In the case of producing the single-phase oxide of the present invention, the EDTA complex polymerization method is preferred.

Here, in FIG. 3, using CaCO ₃ , Al ₂ O ₃ , and Mn ₂ O ₃ as starting materials, synthesis was performed by solid phase reaction (in a nitrogen atmosphere at 1250 ° C. for 24 hours, further for 24 hours, main firing). An X-ray diffraction pattern of Ca ₂ AlMnO _5.0 (above), and CaCO ₃ , Al, and Mn ₂ O ₃ were used as starting materials and synthesized by an EDTA complex polymerization reaction (in the air, main firing at 1250 ° C. for 24 hours). An X-ray diffraction pattern (bottom) of Ca ₂ AlMnO _5.0 is shown.

From the X-ray diffraction pattern (top) of FIG. 3, when synthesized by solid phase reaction using CaCO ₃ , Al ₂ O ₃ , and Mn ₂ O ₃ as starting materials, the main phase Ca ₂ AlMnO _{5 + δ} In addition, it can be seen that rock salt-type (Mn _1-x Ca _x ) O is generated as an impurity (see circles in the figure). This is presumably because unreacted Ca—Mn oxide remained because the reactivity of Al ₂ O ₃ was poor.

On the other hand, the present invention oxide, when synthesized in EDTA complex polymerization method, as shown in X-ray diffraction pattern of FIG. 3 (bottom), X-ray diffraction peaks indicating impurities not all, Ca ₂ AlMnO 5 ₊ δ X-ray diffraction peak.

That is, it can be seen that single-phase Ca ₂ AlMnO _{5 + δ} could be synthesized by the EDTA complex polymerization method. When the crystal structure of this Ca ₂ AlMnO _{5 + δ} was indexed assuming an orthorhombic Ibm2 unit cell, the lattice constants were a = 5.462Å, b = 14.93Å, and c = 5. .241 cm (see FIG. 3).

Next, in order to investigate the oxygen absorption / release characteristics of the synthesized single-phase Ca ₂ AlMnO _{5 + δ} , Ca ₂ AlMnO _{5 + δ} is heated and cooled in an oxygen stream to give a thermal history, and the weight change It was measured. The result is shown in FIG.

When Ca ₂ AlMnO _{5 + δ} is heated in an oxygen stream at 2 ° C./min, the weight starts to increase from around 250 ° C. and becomes maximum at around 450 ° C. as shown in FIG. The weight change ΔW at this time is 2.5%, and the oxygen absorption amount δ can be estimated to be 0.38. Furthermore, when the temperature continues to be increased, the weight rapidly decreases around 600 ° C. Thereafter, the weight of Ca ₂ AlMnO _{5 + δ} gradually decreases until reaching 800 ° C.

When Ca ₂ AlMnO _{5 + δ} is heated to 800 ° C. in an oxygen stream and then cooled down at 2 ° C./min, oxygen is absorbed and the weight increases greatly at around 550 ° C. After the weight increases, the weight of Ca ₂ AlMnO _{5 + δ} is almost saturated below 400 ° C. The amount of oxygen _δ of Ca ₂ AlMnO _{5 + δ} estimated from the change in weight is δ≈0.38.

Here, FIG. 5 shows X-ray diffraction patterns of Ca ₂ AlMnO _{5 + δ} before and after thermogravimetric analysis. In the figure, the upper is an X-ray diffraction pattern before thermogravimetric analysis, and the lower is an X-ray diffraction pattern after thermogravimetric analysis.

The X-ray diffraction pattern of Ca ₂ AlMnO _{5 + δ} (oxygen absorption phase) after thermogravimetric analysis could be indexed with a structural model (space group Imma) with δ = 0.5 (Patent Document 10). ,reference). The lattice constants were a = 5.232 Å, b = 29.42 Å, and c = 5.370 （(see FIG. 5).

That is, from FIG. 5, by heat treatment in an oxygen stream, Ca ₂ AlMnO _{5 + δ} (δ≈0) (refer to (a) in FIG. 2) having a crystal structure of Ibm2 absorbs oxygen and has a basic skeleton structure. It can be seen that the crystal structure changed to Ca ₂ AlMnO _{5 + δ} (δ≈0.38) (see (b) in FIG. 2) having the crystal structure Imma.

The present inventors further investigated the reversibility and rapidity of oxygen absorption / release of Ca ₂ AlMnO _{5 + δ} . The reversibility and rapidity of oxygen absorption / release is an important characteristic as a characteristic of a ceramic material for oxygen storage or oxygen selective membrane.

In order to investigate the above characteristics of Ca ₂ AlMnO _{5 + δ} , the inventors set the atmosphere temperature to 500 ° C., switched the atmosphere alternately between a nitrogen atmosphere and an oxygen atmosphere, and performed thermogravimetric analysis. The result is shown in FIG. The weight change is shown on the vertical axis as a weight change (increase or decrease) rate ΔW (%).

From FIG. 6, it can be seen that the weight of Ca ₂ AlMnO _{5 + δ} (δ≈0) immediately increases in the oxygen atmosphere and decreases immediately when the atmosphere is switched to the nitrogen atmosphere. That is, Ca ₂ AlMnO _{5 + δ} is a substance that absorbs or releases oxygen reversibly and rapidly according to the surrounding atmosphere. Therefore, it can be concluded that Ca ₂ AlMnO _{5 + δ} has excellent oxygen absorption / release (oxygen storage) characteristics, and this is the knowledge forming the basis of the present invention.

The weight change rate ΔW (%) of Ca ₂ AlMnO _{5 + δ} by switching the atmosphere is about 2.2%. This value corresponds to an oxygen change amount Δδ = 0.33. Since the maximum oxygen amount of Ca ₂ AlMnO _{5 + δ} is δ = 0.5, about 2/3 of oxygen is absorbed or released.

  Here, FIG. 7 shows changes in ΔW when the oxide of the present invention is repeatedly heated between 500 ° C. and 600 ° C. in an oxygen stream. From FIG. 7, it is understood that the oxide of the present invention has a function of absorbing and releasing a large amount (2 wt%) of oxygen only by a temperature change, unlike the oxygen absorption / release function of CZ or the like. In this respect, the oxide of the present invention is substantially different from known oxygen storage materials.

In the oxide Ca ₂ AlMnO _{5 + δ} of the present invention, oxygen absorption / release phenomenon appears only in a low temperature range of 400 to 600 ° C. and only by temperature change without using a strong reducing atmosphere (see FIG. 4). Therefore, the oxide of the present invention is a substance having an excellent oxygen storage capacity (OSC = 2.5) exceeding the oxygen storage capacity (OSC = 2.2) of CeO ₂ —ZrO _{2 in} a practical temperature range. .

The absorption / release phenomenon of oxygen that is excellent in reversibility of Ca ₂ AlMnO _{5 + δ} and is rapidly expressed is a phenomenon that has not been known so far, and Ca ₂ AlMnO _{5 + δ} is used for oxygen storage or oxygen selective membranes. It is shown to be a practically useful substance as a ceramic material.

The oxygen storage ability of Ca ₂ AlMnO _{5 + δ} has been described above. The manganese oxide of the present invention is a manganese oxide that can be expressed by the following formula (1).

(Ca _2−x A _x ) (Mn _2−y B _y ) O _{5 + δ} (1)
Here, A: one or more of alkaline earth metals other than Ca
B: One or more of Al, Fe, Co, and Ga
0 ≦ x ≦ 2
0 ≦ y <2
0 ≦ δ ≦ 0.5

  A plurality of elements can enter the A site. Ca can be substituted with one or more of alkaline earth metals other than Ca. The alkaline earth metal other than Ca is preferably Sr. The substitution amount x can be all, but is preferably x <1 and more preferably x <0.5 in order to promote the formation of a layered structure. It is more advantageous in terms of cost to contain abundant Ca, which is abundant in resources, and since the weight per mole is light, x≈0 is most preferable in these respects. The A site can be doped with a small amount of rare earth elements.

A plurality of elements can also enter the B site. Mn is an essential element, but Mn can be substituted with one or more of Al, Fe, Co, and Ga. The substitution amount x is preferably 1.5 or less, more preferably x≈1. That is, the oxide of the present invention exhibits the maximum oxygen absorption / release characteristics when Mn ₁ Al ₁ is used.

  The amount of oxygen δ is 0 to 0.5. When δ is 0, the composition has only a skeleton structure that does not contain excess oxygen. When δ is 0.5, the composition is such that half of the oxygen deficient sites in the crystal structure are buried. The oxygen amount δ continuously changes in the range of 0 to 0.5 according to the atmosphere and temperature.

  The oxide of the present invention has unique oxygen absorption / release characteristics and excellent oxygen storage capacity, and thus can be used in various technical fields. For example, the oxide of the present invention can be used as a catalyst material for exhaust gas purification, a positive electrode material of a solid oxide fuel cell, and a ceramic material.

  In addition, the oxide of the present invention can be used for oxygen storage and / or separation. Furthermore, if the oxide of the present invention is used, an oxidation reaction device that performs an oxidation reaction using stored oxygen, a heating / cooling material that performs heating / cooling using heat generation / endotherm associated with oxygen absorption / release, and the heating A heating / cooling device including a coolant and an oxygen removing device that removes oxygen gas present in the container can be configured.

  Next, examples of the present invention will be described. The conditions adopted in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is an example of this one condition. It is not limited to. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

Example 1
Ca ₂ AlMnO _{5 + δ} was synthesized by EDTA complex polymerization method using CaCO ₃ , Al (powder) and Mn ₂ O ₃ as raw materials. CaCO ₃ , Al, and Mn ₂ O ₃ powders were dissolved in concentrated nitric acid at a ratio of Ca: Al: Mn = 2: 1: 1, and complexed by adding an EDTA / NH ₃ solution. The molar ratio of EDTA to metal ions was 1.5: 1.

  The pH of the EDTA complex solution was adjusted to pH = 9, heated to about 120 ° C., dried and burned to produce a porous combustion product (precursor). This combustion product was calcined in air at 450 ° C. for 1 hour, and further calcined in air at 1250 ° C. for 24 hours.

The obtained Ca ₂ AlMnO _{5 + δ was} subjected to phase identification and structural analysis by X-ray diffraction. The result is as shown in the X-ray diffraction pattern (bottom) of FIG.

(Example 2)
The oxygen absorption / release characteristics of Ca ₂ AlMnO _{5 + δ} obtained in Example 1 were evaluated. This Ca ₂ AlMnO _{5 + δ} is heated up to 800 ° C. at 2 ° C./min in an oxygen stream, and then lowered to 200 ° C. or less at 2 ° C./min. Was measured with a thermobalance. The measurement results are as shown in FIG.

X-ray diffraction was performed on Ca ₂ AlMnO _{5 + δ} after thermogravimetric analysis. The X-ray diffraction pattern is as shown in FIG. 5 (see X-ray diffraction pattern below).

Since the lattice constants of Ca ₂ AlMnO _{5 + δ} after thermogravimetric analysis are a = 5.232 Å, b = 29.42 Å, and c = 5.370 Å, Ca ₂ AlMnO _{5 + δ} is heat treated in an oxygen stream. in, Ca ₂ AlMnO _{5 + δ} crystal structure Ibm2 (δ ≒ 0) is to absorb oxygen, while the basic skeleton structure is _{unchanged, Ca 2 AlMnO 5 + δ (} δ ≒ 0.38) of crystal structure Imma It turns out that it changed to.

(Example 3)
Ca ₂ AlMnO _{5 + δ} obtained in Example 1 was set to 500 ° C., and the atmosphere was alternately switched between nitrogen and oxygen, and thermogravimetric analysis was performed. The result is as shown in FIG. From FIG. 6, it is understood that Ca ₂ AlMnO _{5 + δ} is a substance that reversibly and rapidly absorbs or releases oxygen in accordance with the surrounding atmosphere.

The weight change rate ΔW (%) of Ca ₂ AlMnO _{5 + δ} by switching the atmosphere is about 2.2%. This value corresponds to an oxygen change amount Δδ = 0.33. Since the maximum oxygen amount of Ca ₂ AlMnO _{5 + δ} is 0.5, about 2/3 of oxygen is absorbed or released.

Example 4
The Ca ₂ AlMnO _{5 + δ} obtained in Example 1 was heated by repeatedly changing the temperature between 500 ° C. and 600 ° C. in an oxygen stream and subjected to thermogravimetric analysis. The result is as shown in FIG. From FIG. 7, it can be seen that Ca ₂ AlMnO _{5 + δ} has a function of absorbing and releasing oxygen only by temperature change, which is substantially different from CZ.

As described above, the manganese oxide “(Ca _2−x A _x ) (Mn _2−y B _y ) O _{5 + δ} (δ: 0 ≦ δ ≦ 0.5)” of the present invention is a temperature change only. Since it has the function of absorbing and releasing oxygen, in addition to catalytic materials for exhaust gas purification, catalytic materials for redox, positive electrode materials for solid oxide fuel cells, oxygen storage, oxygen separation, oxygen removal, oxygen selection, And / or it is an optimal substance as a material for oxygen enrichment.

  Further, the manganese oxide of the present invention is a promising substance as an inexpensive practical material that replaces CZ containing expensive Ce because it contains abundant elements as resources. Therefore, the present invention has great industrial applicability.

Claims (2)

A method for storing and / or separating oxygen using a brown mirrorlite type manganese oxide of the following formula (1) , wherein the temperature is repeatedly changed in a temperature range of 400 to 600 ° C. A method for storing and / or separating oxygen, wherein the amount of oxygen is changed and the oxygen is stored and / or separated in a range of more than 0 to 10 mol% with respect to the total oxygen molar amount.
(Ca _2−x A _x ) (Mn _2−y B _y ) O _{5 + δ} (1)
Here, A: one or more of alkaline earth metals other than Ca
B: One or more of Al, Fe, Co, and Ga
0 ≦ x ≦ 2
0 ≦ y <2
0 ≦ δ ≦ 0.5 2. The oxygen storage / separation method according to claim 1, wherein x and y are 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1, respectively.